Auxiliary resonant commutated pole converter with voltage balancing circuit

Abstract

A resonant power converter is provided. The resonant power converter comprises a balancing circuit for balancing the voltage in a feeding connection. The balancing circuit comprises: a first positive control means in series with an inductor, wherein the first positive control means and the inductor is coupled between the positive DC conductor and the feeding connection, and a second negative control means in series with the inductor, wherein the second negative control means are coupled between the negative DC conductor and the feeding connection. The first positive and second negative control means are adapted to be alternatingly switched on and off for balancing the resonant power converter, such that the voltage in the feeding connection is substantially the mean voltage of the positive DC conductor and the negative DC conductor.

The invention claimed is: 
     
       1. A resonant power converter comprising:
 a DC power source; 
 a positive DC conductor; 
 a negative DC conductor; 
 a phase conductor; and 
 a power converting unit coupled between the DC power source and the phase conductor, the power converting unit comprising:
 a first switch coupled between the positive DC conductor and the phase conductor and a first diode connected in parallel with the first switch, 
 a second switch coupled between the negative DC conductor and the phase conductor and a second diode connected in parallel with the second switch, and 
 a resonant auxiliary switching circuit coupled between a feeding connection on the DC power source and the phase conductor, the resonant auxiliary switching circuit comprising a control for controlling a current flow through the resonant auxiliary switching circuit between the feeding connection and the phase conductor; a balancing circuit for balancing a voltage in the feeding connection, the balancing circuit comprising:
 a first positive control in series with an inductor, wherein the first positive control and the inductor are coupled between the positive DC conductor and the feeding connection, and 
 a second negative control in series with the inductor, wherein the second negative control is coupled between the negative DC conductor and the feeding connection, 
 
 wherein the first positive and second negative controls are configured to be alternatingly switched on and off for balancing the resonant power converter, such that the voltage in the feeding connection is substantially a mean voltage of the positive DC conductor and the negative DC conductor. 
 
 
     
     
       2. The resonant power converter according to  claim 1 , further comprising an auxiliary capacitor coupled in parallel with an inductor such that a parallel resonant circuit is created when a current flows through the resonant auxiliary switching circuit. 
     
     
       3. The resonant power converter according to  claim 1 , further comprising an auxiliary capacitor coupled in series with an inductor such that a series resonant circuit is created when a current flows through the resonant auxiliary switching circuit. 
     
     
       4. The resonant power converter according to  claim 1 , wherein the first positive control and the second negative control are connected in series with a single inductor, in turn coupled to the feeding connection. 
     
     
       5. The resonant power converter according to  claim 1 , wherein the positive and negative controls are adapted to be controlled along with the switches. 
     
     
       6. The resonant power converter according to  claim 5 , wherein the switching of the first switch and the first positive control is adapted to be synchronized, and the switching of the second switch and the second negative control is adapted to be synchronized. 
     
     
       7. The resonant power converter according to  claim 1 , wherein the first positive and second negative controls are adapted to be alternatingly switched such that the first positive control is on substantially 50 percent of the time and off substantially 50 percent of the time, and the second negative control is on substantially 50 percent of the time and off substantially 50 percent of the time. 
     
     
       8. An active filter comprising the resonant power converter of  claim 1 . 
     
     
       9. An active filter for reducing harmonics in an electrical system, the active filter comprising the resonant power converter of  claim 1  and further comprising a control unit configured to:
 measure at least one of voltage or current at a point in the electrical system, and 
 control the switches of the resonant power converter based on the measured at least one of voltage or current. 
 
     
     
       10. The active filter according to  claim 9 , wherein the control unit is further configured to control the first positive and second negative controls of the resonant power converter for balancing the DC power source of the resonant power converter. 
     
     
       11. The active filter according to  claim 10 , wherein the control unit is further configured to control the switches and first positive and second negative controls such that the switching of the first switch and the first positive control is synchronized, and the switching of the second switch and the second negative control is synchronized.